A project to design a field desorption source for an MS-9 mass spectrometer has been continued. Useful field ionization mass spectra have been obtained with this source. The uses of stable isotopes in biomedicine have been explored. Syntheses of carbon-13 labelled alkanes, deuterium labelled serotonin and melatonin, and deuterium labelled imipramine and desipramine have been completed.